1. Field of the Invention
The present invention relates to an optical lens barrel and an image pickup apparatus including the optical lens barrel.
2. Description of the Related Art
Conventionally, the tip of the lens barrel (optical lens barrel) of a compact camera is provided with lens barriers (hereinafter, referred to as “barriers”) that automatically open/close to protect the lens during the camera being not used. For a common barrier driving method, movement of the lens barrel in the optical axis direction is converted to movement in the turning direction to make a barrier driving member turn around the optical axis, thereby opening/closing the barriers. A typical configuration is shown in, for example, FIG. 5 in Japanese Laid-Open Patent Publication (Kokai) No. 2006-098486.
This mechanism is configured so that, when an actuating member moves in the optical axis direction and a cam surface of the actuating member abuts on a cam section included in a base member, the actuating member turns around the optical axis.
This mechanism has advantages in that: the cam section extends out from a fixed member, easily ensuring a sufficient strength; and backlash occurs in the actuating member, suppressing loss in driving force transmission and variation in timing.
Normally, an intermediate barrel, which has a shutter and a diaphragm (or ND filter), is located between a front barrel that holds the barrier mechanism and the base member. The aforementioned cam section extends through this intermediate barrel, and thus, the shutter and the diaphragm are inevitably arranged in positions avoiding the cam section, resulting in limitation on the degree of freedom of design.
Also, conventionally, a rearmost lens group is often used as a focusing lens that moves in the optical axis direction. A guiding member and a feed screw for moving the focusing lens extend in the optical axis direction in the rearmost barrel that holds the focusing lens. Thus, when the intermediate barrel moves toward the focusing lens to reduce the entire lens barrel length during the camera being not used, the aforementioned guiding member and feed screw overlap with the intermediate barrel. Therefore, a clearance structure is provided at a part of the intermediate barrel, and no other mechanism parts can be arranged at that part.
In addition, in recent years, an image stabilization mechanism that stabilizes an image moved due to hand shake by moving a part of the lens in the direction to cancel the movement out is often employed. However, since such image stabilization mechanism is also arranged in the aforementioned intermediate barrel, it becomes further difficult to make a compact layout of the respective components.
Meanwhile, another barrier driving method in which turning movement of a rotation cylinder included in a lens barrel is transmitted to an actuating member to drive the actuating member to turn is also conventionally employed. This method has a problem in that large transmission loss occurs in the system for transmitting a driving force from a drive source (motor) to the rotation cylinder and also large backlash occurs, resulting in variation in drive timing easily occurring.
Accordingly, as mentioned above, there is a demand to efficiently lay out a shutter, a diaphragm and an image stabilization mechanism to achieve downsizing in a system in which a fixed member directly drives an actuating member to turn.